CFM 56 engines do not leak. If it does, there is something wrong.
I do not consider an oil leak a consumption issue. I know there are limitations when it comes to leaks (from the different drains), normally x number of drops
pr minute.
My own procedures are as follows:
If there is a small leak, I'll enter it in the log, and the engineer must sign it off as within limits, checked, no leak found, or whatever. I will monitor the engine for the remaining sectors. The information will then be available to the next crew if they bother to check the log for the previous flight(s).
If there is a pool of oil under the engine, I'm not going before it is fixed. Simple as that. They can throw manuals and limitations at me all they want, I don't care. If management pilots have any objections, then they can take the dodgy engine on the night ETOPS, over water, flight themselves. Not likely, as you never see them on those flights will perfect aircraft either.
Each and every time I spot a leak, I'm told "Its normal", or "the engine will always discard some oil during shut down", or "we spilled some oil when we topped it up", or something to that effect. And every time I have refused the aircraft, they have found something wrong with it.
The crew on that MD-80 (some years ago) that blew one engine on take off, killing some passengers, also spotted an oil leak under the "bad" engine. I believe they were charged with man slaughter after that accident.
I work with engineering, but with caution.